Common Accidents on the Site of High-speed Steel Rolling and Measures (2)

5. What are the reasons for holding back the steel during rolling?

(1) Defects caused by the billet itself, such as inclusions, delamination, severe bubbles, etc., are rolled to half during the rolling process, causing cracking and holding the steel;

(2) When the speed of the certain intermediate rolling mill is set improperly, the steel rolling state is actually produced. The first half of the rolled piece is maintained by the front rolling mill to maintain tension rolling. When the tail of the rolled piece leaves the front rolling mill, the tension suddenly loses there, causing the holding back of steel;

(3) It is caused by the sudden increase or decrease of the speed of the motor of a rolling mill, which destroys the original continuous rolling relationship;

(4) Due to the sudden breakage of the roll or the severe damage of the guide in the previous passes, the cross-section of the rolled piece is changed and the steel is held.

Measures: ① Strengthen the picking of raw materials, strengthen the inspection of steel rolling, and take timely measures;

② Eliminate excessive tension;

③ Notify electrical treatment;

④ Regularly shut down to check the wear of the rolling guide to avoid holding back the steel.

6. Adjustment of the intermediate rolling mill unit: When adjusting the material type, you must first pay attention to the state of the stacking steel between the two rolling mills, and then adjust the ellipse material type. You must pay attention to whether the input splint is seriously worn.

7. Heavy iron hitting at the outlet of the rough and medium rolling mill:

(1). The front frame round hole material is too full or the input guide wears seriously (With severe scratches).

(2). The material type of this frame is inappropriate and too large.

(3). Change the exit guide.

8. Pre-finishing rolling mill: (1) 14 output is seriously ironed: the incoming material is too large, the amount of reduction is too large; the material shape is wide; the inner wall of the exit guide is not smooth, and the grinding is not good.

(2) 15 input is severely ironed: 14 outlets are worn and the torsion angle is not suitable; 15 inlet guide guard gaps are not suitable or severely worn and cannot support the steel;

(3) 15 input guide roller: the input guide is not installed correctly, and the incoming material hits the single-side guide roller when biting; the guide gap is not suitable, too tight; the guide roller is not cooled.

9. 17, 19 guide guard hit iron:

Measures: The guide gap is small, and press the 16, 18 material to re-find the tension.

10. Pre-finishing rolling leaving tail

Reasons: Tension before continuous finishing (continuous adjustment), the material shape is not good.

Measures: After pressing the material to the standard value, adjust the tension again; the delay time of the looper is not suitable; the height of the looper is not suitable.

11. 3# Shear steel pile

(1) Head pile steel

Reason: cutting head of 3# is too short, bring the head into 7 sets; 3# shear is without the head.

Measures: Lengthen the cutting head of 3# shear.

(2) Steel pile in the middle or tail

Reason: The pre-finishing rolling speed is set too high continuously.

Measures: adjustment to reduce pre-finishing 5 consecutive adjustments.

More Articles You May Be Interested:

1. The Main Factors Affecting the Quality of the Wire Rod 

2. How to Improve the Assembly Quality of the Roller Box of the Wire Rod Mill?

3. Process Adjustment of Wire Rod Mill

4. Technical Requirements of Rolls and Reasons for Broken Rolls 

5. Finishing Mill Roll Assembly Technology

6. The Practice of Direct Rolling without Heating

Common Accidents on the Site of High-speed Steel Rolling and Measures (1)

1. Jamming of steel

Reasons: ① The roll gap on both sides of the roll is inconsistent.

② The gap of the input box is severely worn, the gap is too large.

③ The axially fixed pressing block of the roll is not fastened, which causes roll error in rolling.

④ Incoming materials are out of square or severely reversed.

⑤ Long-term wear of the hole type is on the left or right side.

Measures: ① Adjust roll gap;

② Replace the input box;

③ Tighten the axial fixed pressure block to eliminate the roller error;

④ Remove the raw materials with serious detachment;

⑤ Change the slot.

2. Rolled piece do not bite

Reasons: ① The reduction is too large;

② The grinding groove is not good or there are water and oil on the surface of the groove;

③ The sliding plate on the inner side of the card-breaking shear is not welded or moved laterally;

④ The head of the incoming material is off square or has a large deformation during cutting, and it is stuck in the input box.

Measures: ① Reduce the reduction of this pass, enlarge the roll gap appropriately, and then press back to the normal range after normal rolling, the billet head is cut into a wedge or cone shape, when changing the roll or groove (When the rolling stop time is sufficient), press the head of the billet a little bit in advance, stop the machine and then go out of the rolling mill and return to the heating furnace to reheat.

② Grind the grooves in place to increase the surface roughness of the grooves and remove oil stains;

③ Check the shearing machine and rolling mill processing;

④ Remove the raw materials with severe head deformation or cutting.

3. Rough and medium-rolled slipping steel

Reasons: ① The reduction is too large;

② The grinding groove is not in place;

③ Turn on the cooling water in advance;

④ There is oil on the surface of the groove;

⑤ The gap between input guides is small;

⑥ The speed of the front frame has not been reduced (2.5% ～ 3%) just after the rolling.

Measures: ① Properly enlarge the roll gap and press it back to the normal range after normal rolling;

② Grinding groove in place;

③ Avoid turning on the cooling water in advance;

④ Remove the oil stain on the surface of the rolling groove;

⑤ Check the gap between the input guides;

⑥ Slow down after changing the roller and groove.

4. Head rolling steel during rolling

Reasons: ① The size of the rolled product in the previous pass is too large, so that when the rolled product enters the next pass, it is squeezed in the entrance guide plate to cause suffocation;

② Due to the uneven deformation of the billet head during rolling, the temperature of the billet head is low may cause the steel to split;

③ The rolling guide is seriously worn, the guide roller does not rotate, and the guide roller arm is loose, which causes the guide roller gap to change, causing steel holdback;

④The elbow of the rolled piece does not lead to the next lane, causing steel holdback.

Measures: ① Adjust the material type;

② Avoid low-temperature steel, pay attention to the condition of the billet head and avoid splitting the head;

③ Regular shut down to check the input and output guide to avoid holding back the steel;

④ Avoid elbows;

What we can do:

We are specialized in manufacturing high-speed morgan wire rod mill, high-speed rebar rolling mill, TMT rolling mill, high-speed gearbox, hard-faced gearbox.
We also provide complete design for your rolling mill workshop, not only turnkey project but also tailor-made service.

And we provide all the parts for roughing rolling mill, intermediate rolling mill process, including pinch roll, all kinds of shears, laying head, all of these crucial parts work extremely precisely and reliably.


If necessary, please feel free to contact me. Email: marketing2@hanrm.com

Reasons and Solutions for the Piling of Wire Rod Rolling

1. Piling of Steel Head

The Reason:

1) The friction of the rolling groove after changing the roll and groove is too small, causing the head of the rolled product to slip;

2) The head of the rolled product is tilted out of the rack, causing it to fail to bite into the downstream rack or the head guide position smoothly;

3) There are foreign objects in the rolling groove or guide groove;

4) The billet is severely out-of-square, unable to enter the rolling mill or take out the outlet pipe;

5) The blank is split out of the guide or wrapped around the roller.

Solution:

1) Increase the groove friction when changing rolls and grooves. Grind the grooves with the grinder or use spot welding, and turn off the cooling water of the rolls until they are completely bitten.

2) Check whether the guide base is loose and whether the rolling line is centered, and replace the old guide in time.

3) In the rolling process, timely clean up the oxide scale;

4) In the rolling process, unqualified billets are removed in time, and splitting occurs. Emergency stops should be taken as soon as possible to reduce the waste steel processing time.


2. Piling of the Middle and End of the Rolled Piece

The Reason:

1) Due to improper roll gap setting caused by improper size of rolled products, stacking steel;

2) Defects of the billet, such as inclusions, bubbles, etc., are broken during the rolling process and cause stacking of steel;

3) The speed of the rolling mill is improperly designed, and it is in the state of stacking and rolling. When the first half of the rolled product is maintained by the front rolling mill to maintain micro-tension rolling, when the tail of the rolled product leaves the front rolling mill, the tension is suddenly lost there, causing the stack at the stand tail;

4) Sudden increase or decrease in speed of the rack motor caused the stacking of steel;

5) The roll was suddenly broken or the guides were severely damaged in the first few passes, which caused the stacking of steel.


Solution:

1) After changing rollers and grooves, accurately set the groove bottom, correctly measure the diameter and speed of the rollers, and reduce speed errors

2) Strengthen the inspection of unqualified blanks;

3) Correctly adjust the tension between each frame;

4) Inspect electrical equipment and replace damaged electrical components;

5) Check the amount of roll cooling water, adjust the steel temperature, and prohibit rolling of low temperature steel and blackhead steel.


3. Piling steel between Finishing Mill Stands

The Main Reason:

1) The guide wheel does not rotate or the bearing burns;

2) splits of rolled products;

3) The guide or roller ring is incorrectly installed;

4) Improper roll gap setting or improper incoming size;

5) the roller ring is broken;

6) The broken line causes the rolling line to break automatically.


Solution:

1) Replace the guide, and strengthen the correctness of the guide installation;

2) Strengthen the blank inspection and lengthen the cutting head;

3) Recheck and adjust the roll gap;

4) Replace the roller ring and check the cooling water pipe at the same time;

5) Check the switch at the fishing line pendant, check whether there is scrap steel in the guide of the finishing mill. If there is any, it means that the previous one has piled steel in the finishing mill, and reset the roll gap in the finishing mill.

What we can do:

We are specialized in manufacturing high-speed morgan wire rod mill, high-speed rebar rolling mill, TMT rolling mill, high-speed gearbox, hard-faced gearbox.

We also provide complete design for your rolling mill workshop, not only turnkey project but also tailor-made service.

And we provide all the parts for roughing rolling mill, intermediate rolling mill process, including pinch roll, all kinds of shears, laying head, all of these crucial parts work extremely precisely and reliably.

If necessary, please feel free to contact me. Email: marketing2@hanrm.com

Classification and Development of Direct Rolling and Hot Feeding

The real direct rolling is to roll the continuous casting slab sent from the continuous casting machine directly into the final product without any other heating or heating process. However, for many years, most of the production process research and tests for producing high-quality products have reheated or reheated the continuous casting slab before rolling.

Continuous casting slab hot feeding and hot charging and direct rolling technology are new technologies under development, and the specific characteristics are as follows:

Continuous casting slabs are directly rolled without heating or supplemental heating, referred to as CC-FDR, and are classified into 1 type. Under the condition that the surface temperature is above 820 ° C (the core is above 960 ° C), the continuous casting slab is directly sent to the rolling mill without any form of heating and supplemental heating, and without building a heating furnace. The slab has not undergone the γ-α-γ phase transformation recrystallization process before rolling, and the as-cast coarse austenite grains are still retained. The trace elements Nb and V do not have the precipitation and re-dissolution processes in conventional cold-loading furnaces, so they must be developed. A new rolling process to obtain a grain-refined structure.

Continuous cast slab rolling, referred to as CC-DR, is classified into 2 types. The continuous casting slab is directly sent to the rolling mill through the corner heating device during the conveying process without passing through the heating furnace under the conditions above A3 temperature.

Continuous casting slab hot direct rolling, referred to as CC-HDR, is classified into 3 categories. The continuous slab temperature is above A3. The slab does not pass through the heating furnace. During the conveying process, the rollable temperature is reached by supplementary heating and soaking, and it is directly sent to the rolling mill for rolling.

Continuous hot-rolling of continuous casting slabs, referred to as CC-DHCR, is classified into 4 categories. The continuous casting slab temperature is below A3 and above A1, and the casting slab is directly sent to a heating furnace for heating and rolling. Due to the high temperature of hot charging, it is also called red delivery, and the heating furnace acts as a buffer between the continuous caster and the rolling mill.

Continuous hot-rolling of continuous casting slabs, referred to as CC-DHCR, is classified into 4 categories. The continuous casting slab temperature is below A3 and above A1, and the casting slab is directly sent to a heating furnace for heating and rolling. Due to the high temperature of hot charging, it is also called red delivery, and the heating furnace acts as a buffer between the continuous caster and the rolling mill.

The continuous casting slab cold rolling furnace is heated and rolled, referred to as CC-CCR, and is classified into 6 categories. This is the conventional rolling method when there is no hot-feed and hot-fill process.

Solution to Slow Start of Rolling Mill Machine

The speed at which the rolling mill machine is started during operation has a very important effect on the efficient work of the rolling mill. If the starting speed of the rolling mill machine is slow when it is ready for operation, it means that there is a significant deficiency in the performance of the rolling mill equipment, which will affect the working efficiency of the rolling mill. The force between the billet or rolled product and the roll cannot reach good condition.

The rolled piece cannot be fully rolled in the rolling mill. Under this condition, the power consumption of the rolling mill machine is several times higher than usual. If it happens often, the speed of the rolling mill cannot be effectively started, the efficiency of the billet or rolled product will become lower and lower. For steel rolling mill equipment, if it cannot be started quickly and overloaded, the billet rolling speed will be too slow. Here, let me analyze the reasons and solutions for the slow startup speed.

Before starting the rolling mill machine, it is necessary to verify the power of the equipment motor, rolling speed, product specifications, hole technology, etc., ensuring that the amount of billet retransmission does not exceed the bearing capacity of the rolling mill equipment, otherwise the startup speed of the equipment will slow down. We also need to check the rolling mill bearings to see if the bearings are adequately lubricated. If the lubrication is not sufficient, the rolling mill machine's start-up will also slow down or even malfunction.

More Articles You May Interested:

1. Processing Technology of Parts in High-speed Wire Rod Mill

2. Chemical Elements Affecting Steel Properties

3. Components of the Vertical Rolling Mill

4. Factors Affecting Service Life of Rolling Mill

5. Causes of Piling up of Steel

Repair Method and Operation Process of Rolling Mill Roll

During the operation of the rolling mill, the roll is easy to be damaged. In order to repair the roll body timely and effectively, it is necessary to judge and analyze from the determination of service life, the identification of crack depth, turning crack and other aspects, so that the rolling mill can return to normal.

Because there is no good method to detect the crack depth of the rolling mill roll, the length of service life can only be judged and determined according to the experience, the type of rolling mill, the type of alloy produced and the roughness of the roll surface. According to the theory, the correct service life should be before the crack depth reaches 3 mm, beyond which the roller surface should be grinded, otherwise it is easy to cause the roller sleeve to burst.

In general, if the crack on the rolling mill roll is open, its depth is deeper than tortoise crack or other microcracks, and the crack width is also larger. Therefore, the longest circumferential crack and the widest crack on the roll surface must be found out correspondingly. Through these cracks, the minimum cutting amount can be determined, and the magnetic particle inspection can be used for crack areas.

In order to ensure the safety, the turning depth of the rolling mill roll needs to add 0.5mm to the crack depth in general, and the roughness of the roll surface after turning shall not be less than 6.3; the surface roughness of the roll surface after grinding shall reach 0.8, which can be compared with the standard block or measured with the roughness detector.


When the defects of the rolling mill roll are turned, magnetic particle inspection shall still be carried out to ensure that all micro-cracks have been eliminated. If there are still micro-cracks, turning is still required. It should be noted that every time the repair is made, the record should be made and kept for the daily backup.

More Articles You May Be Interested:

1. Causes and Solutions of Rolling Mill Screw Loosening

2. Why Is the Oil Film Bearing of Finishing Mill Damaged?

3. The Importance of Rolling Mill Rollers

4. What Issues Should Be Paid Attention to When Rolling Mills Are Transported and Stored?

5. Leak Proof Measures for High-Speed Hot Rolling Mill

How to Adjust the Roll Gap?

Adjusting roll hole shape and controlling plate shape are mainly based on rolled products. The rolls are supported and held in a fixed position in the rolling mill. Roller bearings have a large workload and vary widely, so a small coefficient of friction is required.

After determining the products rolled by the rolling mill, the line speed of the rolling mill can be basically confirmed. The hardness of the raw material is measurable. The rolling stock of the rolling mill is determined by changing the plastic deformation size.

How to configure the rolls according to the hole process? Generally, the newly installed rolling mill has a running-in process. During the running-in process, the rolls are run at no load, and the running speed is 50%, 65%, 75%, and 85% in stages. Different rolling mills have different materials and specifications for rolls according to different rolling products.

For example, the continuous casting machine and rolling mill has a daily output of 100 tons and a rolling speed of 15-25 m / s. Rough rolling efficiency accounts for 30% -40%, intermediate rolling efficiency accounts for 50% -60%, and rough rolling efficiency reaches 95%. After the rolling mill is installed, the large and small teeth of the reducer and gearbox need to mesh, the rolling speed is too fast, and the torque is enhanced. After the rolling mill runs normally for 30 consecutive days, stop the rolling mill to check the meshing of the large and small gears. When everything is normal, the rolling speed can be increased.

Under normal circumstances, there is no need to adjust the rolling speed. In the rolling mill, the rolls are constantly worn during operation. In order to maintain the stable operation of the rolling mill when the rolls are under controllable rolling requirements, the rolls must be repaired in time. In severe cases, the rolls need to be replaced.

More Articles You Maybe interested:

1. Factors Affecting Service Life of Rolling Mill

2. Processing Technology of Parts in High-speed Wire Rod Mill

3. Chemical Elements Affecting Steel Properties

4. Rolling Mill Adjustment before Rolling

5. What Are the Key Points of Rolling Mill Hoisting?